1. Field of the Invention
The present invention relates to apparatus for laying flexible pipe in a ditch, and for surrounding the pipe with gravel, sand, or the like. More particularly, the present invention relates to a pipe laying device that positions a flexible pipe at a desired elevation above the floor of a trench and that surrounds the pipe with particulate material that is deposited to cover the pipe with a predetermined depth of particulate material above the uppermost surface of the pipe.
2. Description of the Related Art
Known devices for positioning pipe in a trench include a hopper for carrying gravel or other fill material to be deposited around the pipe, and a guide tube that extends through the interior of the hopper for guiding the pipe that is intended to be laid. For example, in U.S. Pat. No. 4,289,424, which issued Sep. 15, 1981, to Robert J. Shefbuch et al., there is shown and described a pipe laying apparatus in which the hopper has a rearwardly sloping lower wall, and an inclined support tube for supporting the pipe to be laid. The support tube terminates rearwardly of the hopper end wall. The hopper is provided in the form of a rectangular container that has side walls adapted to contact the trench side walls, and the hopper side walls and bottom wall each carry tines for raking the adjacent trench side walls and bottom wall as the hopper is drawn along the ditch.
The upper portions of the side walls of the Shefbuch et al. structure include upwardly and outwardly flaring surfaces to define a substantially funnel-shaped cross section. However, because of the cross-sectional shape of the hopper the depth of the trench within which such a hopper can be used is limited, because of the requirement that the hopper side walls contact the side walls of the trench. Thus, if the trench were, say, 8 or 10 feet deep, the hopper side walls, of necessity, would need to be of least that depth, to permit the outward flaring portions of the hopper side walls to be above ground level. Additionally, the large contact area between the hopper side walls and the trench side walls results in very high frictional drag forces, thereby slowing the pipe installation process and requiring high powered vehicles to pull the hopper along the trench.
The depth below the ground at which a perforated drainage pipe must be positioned varies from one part of the country to another, and depends in large part upon the porosity of the surrounding soil. For example, in parts of Ohio the depth specified by local regulations is of the order of about 3 feet. On the other hand, in Southern Virginia the regulations prescribe the depth to be 3 feet or more.
When constructing a drainage field in an area where the depth of the trench is greater than 5 feet the construction cost rise significantly. For that depth and for greater depths the regulations of the Federal Occupational Safety and Health Administration (OSHA) require that if workers are present in the trench it is necessary that the trench be sloped, or that the sides of the trench be braced or supported in order to prevent a cave-in. However, to provide the required slopes or support renders the pipe installation operation considerably more costly than it would be if such slopes or support structure were not required. Therefore, it is desirable that where drain fields or the like are to be constructed and the depth of the drain trench is greater than 5 feet the pipe installation apparatus be so constructed that it is unnecessary for a person to actually physically be within the trench during the pipe laying and covering operation.
It is an object of the present invention to provide improved apparatus for laying flexible pipe within a trench and for simultaneously burying the flexible pipe within bed of gravel in a single operation.
It is another object of the present invention to provide a flexible pipe laying and covering device that is of simple construction, and that can be employed in ditches having depths ranging from two feet to over twelve feet.
It is a further object of the present invention to provide a flexible pipe laying and covering device that presents a reduced contact area with the side walls of the trench, to reduce the pulling force necessary to draw the device along the trench.
It is a still further object of the present invention to provide a flexible pipe laying and covering device that does not require the presence of workers within the trench.